<!DOCTYPE html>
<html lang="zh-CN">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>DDL语句 | Manor Farm Mysql</title>
    <meta name="generator" content="VuePress 1.7.1">
    <link rel="icon" href="/manor-farm-mysql/pgmanor_mysql.svg">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/katex@0.11.1/dist/katex.min.css">
    <script language="javascript" type="text/javascript" src="https://cdn.bootcdn.net/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script language="javascript" type="text/javascript" src="/manor-farm-mysql/js/MouseClickEffect.js"></script>
    <script language="javascript" type="text/javascript" src="/manor-farm-mysql/js/pgmanor-self.js"></script>
    <meta name="description" content="Mysql学习手册">
    <meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=no">
    
    <link rel="preload" href="/manor-farm-mysql/assets/css/0.styles.7bfce8db.css" as="style"><link rel="preload" href="/manor-farm-mysql/assets/js/app.bbd54b43.js" as="script"><link rel="preload" href="/manor-farm-mysql/assets/js/3.33fa8ee0.js" as="script"><link rel="preload" href="/manor-farm-mysql/assets/js/1.e501e4e7.js" as="script"><link rel="preload" href="/manor-farm-mysql/assets/js/33.ae9d6c1c.js" as="script"><link rel="preload" href="/manor-farm-mysql/assets/js/8.73e907b5.js" as="script"><link rel="prefetch" href="/manor-farm-mysql/assets/js/10.31e485b8.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/11.bd87e4cf.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/12.0fe1282f.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/13.f1de335a.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/14.4a84a4ee.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/15.bc190a07.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/16.3f42a3ab.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/17.f1cad67c.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/18.e8063fee.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/19.068739ed.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/20.2b248747.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/21.4fd4cbc1.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/22.2683cc54.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/23.2e39bbe5.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/24.560a4164.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/25.26555323.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/26.8b7e1943.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/27.0f4ac9a1.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/28.f89ec4c0.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/29.71c751c3.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/30.ad576991.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/31.2746a45e.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/32.b62e21d8.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/34.53969cd0.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/35.3e1a8a01.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/36.eb74300d.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/37.16568451.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/38.9a3bc894.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/39.7aab5a75.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/4.c231685d.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/40.cd44603a.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/41.64d0c11a.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/42.3fb5d657.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/43.d4f19236.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/44.6abd5f31.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/45.eaf7b761.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/46.d891856e.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/5.0292b513.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/6.df2ba939.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/7.3b1acb14.js"><link rel="prefetch" href="/manor-farm-mysql/assets/js/9.5220a7da.js">
    <link rel="stylesheet" href="/manor-farm-mysql/assets/css/0.styles.7bfce8db.css">
  </head>
  <body>
    <div id="app" data-server-rendered="true"><div class="theme-container" data-v-2d5f533b><div data-v-2d5f533b><div id="loader-wrapper" class="loading-wrapper" data-v-d48f4d20 data-v-2d5f533b data-v-2d5f533b><div class="loader-main" data-v-d48f4d20><div data-v-d48f4d20></div><div data-v-d48f4d20></div><div data-v-d48f4d20></div><div data-v-d48f4d20></div></div> <!----> <!----></div> <div class="password-shadow password-wrapper-out" style="display:none;" data-v-59a94c5a data-v-2d5f533b data-v-2d5f533b><h3 class="title" style="display:none;" data-v-59a94c5a data-v-59a94c5a>Manor Farm Mysql</h3> <!----> <label id="box" class="inputBox" style="display:none;" data-v-59a94c5a data-v-59a94c5a><input type="password" value="" data-v-59a94c5a> <span data-v-59a94c5a>已加密!</span> <button data-v-59a94c5a>OK</button></label> <div class="footer" style="display:none;" data-v-59a94c5a data-v-59a94c5a><span data-v-59a94c5a><i class="iconfont reco-eye" data-v-59a94c5a></i> <a target="blank" href="https://pgmanor.gitee.io/blog/" data-v-59a94c5a>密钥</a></span> <span data-v-59a94c5a><i class="iconfont reco-theme" data-v-59a94c5a></i> <a target="blank" href="https://vuepress-theme-reco.recoluan.com" data-v-59a94c5a>vuePress-theme-reco</a></span> <span data-v-59a94c5a><i class="iconfont reco-copyright" data-v-59a94c5a></i> <a data-v-59a94c5a><span data-v-59a94c5a>pgmanor</span>
  
<!---->
2021
</a></span></div></div> <div class="hide" data-v-2d5f533b><header class="navbar" data-v-2d5f533b><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/manor-farm-mysql/" class="home-link router-link-active"><img src="/manor-farm-mysql/pgmanor_mysql.svg" alt="Manor Farm Mysql" class="logo"> <span class="site-name">Manor Farm Mysql</span></a> <div class="links"><div class="color-picker"><a class="color-button"><i class="iconfont reco-color"></i></a> <div class="color-picker-menu" style="display:none;"><div class="mode-options"><h4 class="title">Choose mode</h4> <ul class="color-mode-options"><li class="dark">dark</li><li class="auto active">auto</li><li class="light">light</li></ul></div></div></div> <div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/manor-farm-mysql/zh/guide/" class="nav-link router-link-active"><i class="iconfont reco-api"></i>
  指南
</a></div><div class="nav-item"><a href="/manor-farm-mysql/zh/fix/messageBoard.html" class="nav-link"><i class="iconfont reco-suggestion"></i>
  留言版
</a></div><div class="nav-item"><a href="https://pgmanor.gitee.io/blog/2021/01/10/secret-farm-mysql/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-eye"></i>
  文章密钥
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title"><i class="iconfont reco-qq"></i>
      联系
    </span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>QQ在线</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://wpa.qq.com/msgrd?v=3&amp;uin=2307546059&amp;site=qq&amp;menu=yes" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  pgmanor
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li><li class="dropdown-item"><h4>其他方式</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/manor-farm-mysql/zh/fix/contactUs.html" class="nav-link"><i class="iconfont undefined"></i>
  更多
</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title"><i class="iconfont reco-other"></i>
      友链
    </span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>博客</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://pgmanor.gitee.io/blog/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  pgmanor
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://blog.csdn.net/u011622109" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-csd"></i>
  csdn
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://www.iworkh.com" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  iworkh
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li><li class="dropdown-item"><h4>Vue</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://cn.vuejs.org/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  Vue
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://v1.vuepress.vuejs.org/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  VuePress
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://vuepress-theme-reco.recoluan.com/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  vuepress-theme-reco
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li></ul></div></div><div class="nav-item"><a href="/manor-farm-mysql/zh/fix/donate.html" class="nav-link"><i class="iconfont reco-Coding"></i>
  捐赠
</a></div><div class="nav-item"><a href="https://gitee.com/pgmanor/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-mayun"></i>
  Gitee
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div> <!----></nav></div></header> <div class="sidebar-mask" data-v-2d5f533b></div> <aside class="sidebar" data-v-2d5f533b><div class="personal-info-wrapper" data-v-ca798c94 data-v-2d5f533b><img src="/manor-farm-mysql/pgmanor_mysql.svg" alt="author-avatar" class="personal-img" data-v-ca798c94> <h3 class="name" data-v-ca798c94>
    pgmanor
  </h3> <div class="num" data-v-ca798c94><div data-v-ca798c94><h3 data-v-ca798c94>30</h3> <h6 data-v-ca798c94>文章</h6></div> <div data-v-ca798c94><h3 data-v-ca798c94>26</h3> <h6 data-v-ca798c94>标签</h6></div></div> <hr data-v-ca798c94></div> <nav class="nav-links"><div class="nav-item"><a href="/manor-farm-mysql/zh/guide/" class="nav-link router-link-active"><i class="iconfont reco-api"></i>
  指南
</a></div><div class="nav-item"><a href="/manor-farm-mysql/zh/fix/messageBoard.html" class="nav-link"><i class="iconfont reco-suggestion"></i>
  留言版
</a></div><div class="nav-item"><a href="https://pgmanor.gitee.io/blog/2021/01/10/secret-farm-mysql/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-eye"></i>
  文章密钥
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title"><i class="iconfont reco-qq"></i>
      联系
    </span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>QQ在线</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://wpa.qq.com/msgrd?v=3&amp;uin=2307546059&amp;site=qq&amp;menu=yes" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  pgmanor
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li><li class="dropdown-item"><h4>其他方式</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/manor-farm-mysql/zh/fix/contactUs.html" class="nav-link"><i class="iconfont undefined"></i>
  更多
</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><a class="dropdown-title"><span class="title"><i class="iconfont reco-other"></i>
      友链
    </span> <span class="arrow right"></span></a> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>博客</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://pgmanor.gitee.io/blog/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  pgmanor
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://blog.csdn.net/u011622109" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-csd"></i>
  csdn
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://www.iworkh.com" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  iworkh
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li><li class="dropdown-item"><h4>Vue</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="https://cn.vuejs.org/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  Vue
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://v1.vuepress.vuejs.org/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  VuePress
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li><li class="dropdown-subitem"><a href="https://vuepress-theme-reco.recoluan.com/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont undefined"></i>
  vuepress-theme-reco
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></li></ul></li></ul></div></div><div class="nav-item"><a href="/manor-farm-mysql/zh/fix/donate.html" class="nav-link"><i class="iconfont reco-Coding"></i>
  捐赠
</a></div><div class="nav-item"><a href="https://gitee.com/pgmanor/" target="_blank" rel="noopener noreferrer" class="nav-link external"><i class="iconfont reco-mayun"></i>
  Gitee
  <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></div> <!----></nav> <ul class="sidebar-links"><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading open"><span>初入尘世</span> <span class="arrow down"></span></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/manor-farm-mysql/zh/guide/essentials/e-01-install.html" class="sidebar-link">安装</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-02-ddl-dcl.html" aria-current="page" class="active sidebar-link">DDL语句</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-03-dml.html" class="sidebar-link">DML语句</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-04-sort.html" class="sidebar-link">sort排序</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-05-group.html" class="sidebar-link">group分组</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-06-union.html" class="sidebar-link">union合并</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-07-join.html" class="sidebar-link">join</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-08-transaction.html" class="sidebar-link">事务</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-09-view.html" class="sidebar-link">视图</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-10-procedure.html" class="sidebar-link">存储过程</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-11-function.html" class="sidebar-link">函数</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-12-index.html" class="sidebar-link">索引</a></li><li><a href="/manor-farm-mysql/zh/guide/essentials/e-13-devops.html" class="sidebar-link">运维</a></li></ul></section></li><li><section class="sidebar-group depth-0"><p class="sidebar-heading"><span>千锤百炼</span> <!----></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/manor-farm-mysql/zh/guide/advanced/a-01-introduction.html" class="sidebar-link">本章介绍</a></li><li><a href="/manor-farm-mysql/zh/guide/advanced/a-02-prepare-data.html" class="sidebar-link">数据准备</a></li><li><section class="sidebar-group collapsable is-sub-group depth-1"><a href="/manor-farm-mysql/zh/guide/" class="sidebar-heading clickable router-link-active"><span>原理</span> <span class="arrow right"></span></a> <!----></section></li><li><section class="sidebar-group collapsable is-sub-group depth-1"><a href="/manor-farm-mysql/zh/guide/" class="sidebar-heading clickable router-link-active"><span>优化</span> <span class="arrow right"></span></a> <!----></section></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>百战成神</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <div class="password-shadow password-wrapper-in" style="display:none;" data-v-59a94c5a data-v-2d5f533b><h3 class="title" style="display:none;" data-v-59a94c5a data-v-59a94c5a>DDL语句</h3> <!----> <label id="box" class="inputBox" style="display:none;" data-v-59a94c5a data-v-59a94c5a><input type="password" value="" data-v-59a94c5a> <span data-v-59a94c5a>已加密!</span> <button data-v-59a94c5a>OK</button></label> <div class="footer" style="display:none;" data-v-59a94c5a data-v-59a94c5a><span data-v-59a94c5a><i class="iconfont reco-eye" data-v-59a94c5a></i> <a target="blank" href="https://pgmanor.gitee.io/blog/" data-v-59a94c5a>密钥</a></span> <span data-v-59a94c5a><i class="iconfont reco-theme" data-v-59a94c5a></i> <a target="blank" href="https://vuepress-theme-reco.recoluan.com" data-v-59a94c5a>vuePress-theme-reco</a></span> <span data-v-59a94c5a><i class="iconfont reco-copyright" data-v-59a94c5a></i> <a data-v-59a94c5a><span data-v-59a94c5a>pgmanor</span>
  
<!---->
2021
</a></span></div></div> <div data-v-2d5f533b><main class="page"><div class="page-title" style="display:none;"><h1 class="title">DDL语句</h1> <div data-v-3b7f5bdf><i class="iconfont reco-account" data-v-3b7f5bdf><span data-v-3b7f5bdf>pgmanor</span></i> <i class="iconfont reco-date" data-v-3b7f5bdf><span data-v-3b7f5bdf>2021-01-01</span></i> <i class="iconfont reco-eye" data-v-3b7f5bdf><span id="/manor-farm-mysql/zh/guide/essentials/e-02-ddl-dcl.html" data-flag-title="Your Article Title" class="leancloud-visitors" data-v-3b7f5bdf><a class="leancloud-visitors-count" style="font-size:.9rem;font-weight:normal;color:#999;"></a></span></i> <i class="iconfont reco-tag tags" data-v-3b7f5bdf><span class="tag-item" data-v-3b7f5bdf>ddl</span><span class="tag-item" data-v-3b7f5bdf>dcl</span></i></div></div> <div class="theme-reco-content content__default" style="display:none;"><p>本文主要介绍常用的建库、建表、索引等语句</p> <div id="boxx" data-v-f4ca0dac><div data-v-f4ca0dac><p v-if="true" class="custom-block-title" data-v-f4ca0dac></p> <p v-if="true" data-v-f4ca0dac></p></div></div> <h2 id="_1-sql语句分类">1.SQL语句分类</h2> <p><strong>主要分四类</strong></p> <ul><li>DDL: Data Definition Language 数据库定义语言，用于定义SQL模式、基本表、视图和索引的创建和撤消操作。</li> <li>DML: Data Manipulation Language 数据操纵语言，主要包括数据查询和数据更新</li> <li>DCL: Data Control Language 数据库控制语言 (授权，角色控制等)</li> <li>TCL: Transaction Control Language 事务控制语言</li></ul> <h3 id="_1-1-ddl">1-1.DDL</h3> <p>Data Definition Language 数据库定义语言，不需要<code>commit</code>操作就能生效</p> <p><strong>主要包括以下几个SQL操作：</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token keyword">CREATE</span>
<span class="token keyword">ALTER</span>
<span class="token keyword">DROP</span>
<span class="token keyword">TRUNCATE</span>
<span class="token keyword">COMMENT</span>
<span class="token keyword">RENAME</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h3 id="_1-2-dml">1-2.DML</h3> <p>Data Manipulation Language 数据操纵语言，用于让用户或程序员使用，实现对数据库中数据的操作。</p> <p><strong>主要包括以下几个SQL操作：</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token keyword">SELECT</span>
<span class="token keyword">INSERT</span>
<span class="token keyword">UPDATE</span>
<span class="token keyword">DELETE</span>
<span class="token keyword">MERGE</span>
<span class="token keyword">CALL</span>
<span class="token keyword">EXPLAIN</span> <span class="token keyword">PLAN</span>
<span class="token keyword">LOCK</span> <span class="token keyword">TABLE</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><h3 id="_1-3-dcl">1-3.DCL</h3> <p>Data Control Language 数据库控制语言</p> <p><strong>主要包括以下几个SQL操作：</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token keyword">GRANT</span> 授权
<span class="token keyword">REVOKE</span> 取消授权
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><h3 id="_1-4-tcl">1-4.TCL</h3> <p>Transaction Control Language 事务控制语言</p> <p><strong>主要包括以下几个SQL操作：</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token keyword">SAVEPOINT</span> 设置保存点
<span class="token keyword">ROLLBACK</span>  回滚
<span class="token keyword">SET</span> <span class="token keyword">TRANSACTION</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><h2 id="_2-用户sql">2.用户sql</h2> <p>默认用户是root，一般我们都需要创建自己的用户，因为root的权限太大了。</p> <p>这介绍下如何创建用户并赋权</p> <h3 id="_2-1-登陆">2-1.登陆</h3> <p>首先使用root账户登陆</p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">--登陆</span>
mysql <span class="token operator">-</span>u root <span class="token operator">-</span>p
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><blockquote><p>输入密码</p></blockquote> <h3 id="_2-2-用户">2-2.用户</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 创建用户</span>
<span class="token keyword">create</span> <span class="token keyword">user</span> <span class="token string">'pgmanor'</span><span class="token variable">@'%'</span> identified <span class="token keyword">by</span> <span class="token string">'自己密码'</span><span class="token punctuation">;</span>

<span class="token comment">-- 删除用户</span>
<span class="token keyword">drop</span> <span class="token keyword">user</span> <span class="token string">'pgmanor'</span><span class="token variable">@'%'</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br></div></div><h3 id="_2-3-赋权">2-3.赋权</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 赋所有权限 to</span>
<span class="token keyword">grant</span> <span class="token keyword">all</span> <span class="token keyword">privileges</span> <span class="token keyword">on</span> <span class="token operator">*</span><span class="token punctuation">.</span><span class="token operator">*</span> <span class="token keyword">to</span> <span class="token string">'pgmanor'</span><span class="token variable">@'%'</span><span class="token punctuation">;</span>

<span class="token comment">-- 取消授权 from</span>
<span class="token keyword">revoke</span> <span class="token keyword">all</span> <span class="token keyword">privileges</span> <span class="token keyword">on</span> <span class="token operator">*</span><span class="token punctuation">.</span><span class="token operator">*</span> <span class="token keyword">from</span> <span class="token string">'pgmanor'</span><span class="token variable">@'%'</span><span class="token punctuation">;</span>

<span class="token comment">-- 刷新</span>
flush <span class="token keyword">privileges</span><span class="token punctuation">;</span> 

<span class="token comment">-- 退出</span>
quit
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><blockquote><p>登陆测试<code>mysql -h 127.0.0.1 -P 3306 -u pgmanor -p</code>，输入密码。</p></blockquote> <p>更多的权限细节，请参照官网 <a href="https://dev.mysql.com/doc/refman/8.0/en/grant.html" target="_blank" rel="noopener noreferrer">权限文档<span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></p> <h3 id="_2-4-修改密码">2-4.修改密码</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 修改密码</span>
<span class="token keyword">alter</span> <span class="token keyword">user</span> <span class="token string">'pgmanor'</span><span class="token variable">@'localhost'</span> identified <span class="token keyword">by</span> <span class="token string">'想要设置的密码'</span><span class="token punctuation">;</span>

<span class="token comment">-- 提交</span>
<span class="token keyword">commit</span><span class="token punctuation">;</span>

<span class="token comment">-- 退出</span>
quit
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><blockquote><p>然后在<code>mysql -u pgmanor -p</code>重新登陆，输入新的密码。</p></blockquote> <h2 id="_3-库sql">3.库sql</h2> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 创建数据库</span>
<span class="token keyword">CREATE</span> <span class="token keyword">DATABASE</span> <span class="token keyword">IF</span> <span class="token operator">NOT</span> <span class="token keyword">EXISTS</span> <span class="token punctuation">`</span>manor_farm_mysql<span class="token punctuation">`</span>
<span class="token keyword">DEFAULT</span> <span class="token keyword">CHARACTER</span> <span class="token keyword">SET</span> utf8mb4
<span class="token keyword">DEFAULT</span> <span class="token keyword">COLLATE</span> utf8mb4_general_ci<span class="token punctuation">;</span>

<span class="token comment">-- 删除数据库</span>
<span class="token keyword">DROP</span> <span class="token keyword">DATABASE</span> <span class="token punctuation">`</span>manor_farm_mysql<span class="token punctuation">`</span><span class="token punctuation">;</span>

<span class="token comment">-- 数据库编码格式</span>
<span class="token keyword">show</span> variables <span class="token operator">like</span> <span class="token string">'character_set_database'</span><span class="token punctuation">;</span>

<span class="token comment">-- 修改数据库的编码格式</span>
<span class="token keyword">ALTER</span> <span class="token keyword">DATABASE</span> <span class="token operator">&lt;</span>数据库名<span class="token operator">&gt;</span> <span class="token keyword">character</span> <span class="token keyword">set</span> utf8mb4<span class="token punctuation">;</span>

<span class="token operator">-</span> 切换库
<span class="token keyword">use</span> <span class="token punctuation">`</span>manor_farm_mysql<span class="token punctuation">`</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br></div></div><h2 id="_4-表sql">4.表sql</h2> <p><strong>建表</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 建表并定义索引</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> projectfile
<span class="token punctuation">(</span>
	id <span class="token keyword">INT</span> <span class="token keyword">AUTO_INCREMENT</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件id'</span><span class="token punctuation">,</span>
	fileuploadercode <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">128</span><span class="token punctuation">)</span> <span class="token operator">NOT</span> <span class="token boolean">NULL</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件上传者code'</span><span class="token punctuation">,</span>
	projectid <span class="token keyword">INT</span> <span class="token keyword">COMMENT</span> <span class="token string">'项目id;此列受project表中的id列约束'</span><span class="token punctuation">,</span>
	filename <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">512</span><span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件名'</span><span class="token punctuation">,</span>
	fileurl <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">512</span><span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件下载地址'</span><span class="token punctuation">,</span>
	filesize <span class="token keyword">BIGINT</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件大小，单位Byte'</span><span class="token punctuation">,</span>
	<span class="token comment">-- 主键本身也是一种索引（注:也可以在上面的创建字段时使该字段主键自增）</span>
	<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>id<span class="token punctuation">)</span><span class="token punctuation">,</span>
	<span class="token comment">-- 主外键约束（注:project表中的id字段约束了此表中的projectid字段）</span>
	<span class="token keyword">FOREIGN</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>projectid<span class="token punctuation">)</span> <span class="token keyword">REFERENCES</span> project <span class="token punctuation">(</span>id<span class="token punctuation">)</span><span class="token punctuation">,</span>
	<span class="token comment">-- 给projectid字段创建了唯一索引(注:也可以在上面的创建字段时使用unique来创建唯一索引)</span>
	<span class="token keyword">UNIQUE</span> <span class="token keyword">INDEX</span> <span class="token punctuation">(</span>projectid<span class="token punctuation">)</span><span class="token punctuation">,</span>
	<span class="token comment">-- 给fileuploadercode字段创建普通索引</span>
	<span class="token keyword">INDEX</span> <span class="token punctuation">(</span>fileuploadercode<span class="token punctuation">)</span>
	<span class="token comment">-- 指定使用INNODB存储引擎(该引擎支持事务)、utf8字符编码</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> <span class="token keyword">INNODB</span>
<span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span> <span class="token operator">=</span> utf8 <span class="token keyword">COMMENT</span> <span class="token string">'项目附件表'</span><span class="token punctuation">;</span>

<span class="token comment">-- 建表并定义组合索引</span>
<span class="token keyword">CREATE</span> <span class="token keyword">TABLE</span> projectfile2
<span class="token punctuation">(</span>
	id <span class="token keyword">INT</span> <span class="token keyword">AUTO_INCREMENT</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件id'</span><span class="token punctuation">,</span>
	fileuploadercode <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">128</span><span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件上传者code'</span><span class="token punctuation">,</span>
	projectid <span class="token keyword">INT</span> <span class="token keyword">COMMENT</span> <span class="token string">'项目id;此列受project表中的id列约束'</span><span class="token punctuation">,</span>
	filename <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">512</span><span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件名'</span><span class="token punctuation">,</span>
	fileurl <span class="token keyword">VARCHAR</span><span class="token punctuation">(</span><span class="token number">512</span><span class="token punctuation">)</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件下载地址'</span><span class="token punctuation">,</span>
	filesize <span class="token keyword">BIGINT</span> <span class="token keyword">COMMENT</span> <span class="token string">'附件大小，单位Byte'</span><span class="token punctuation">,</span>
	<span class="token comment">-- 主键本身也是一种索引（注:也可以在上面的创建字段时使该字段主键自增）</span>
	<span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span>id<span class="token punctuation">)</span><span class="token punctuation">,</span>
	<span class="token comment">-- 创建组合索引</span>
	<span class="token keyword">INDEX</span> <span class="token punctuation">(</span>fileuploadercode<span class="token punctuation">,</span> projectid<span class="token punctuation">)</span>
	<span class="token comment">-- 指定使用INNODB存储引擎(该引擎支持事务)、utf8字符编码</span>
<span class="token punctuation">)</span> <span class="token keyword">ENGINE</span> <span class="token operator">=</span> <span class="token keyword">INNODB</span>
<span class="token keyword">DEFAULT</span> <span class="token keyword">CHARSET</span> <span class="token operator">=</span> utf8 <span class="token keyword">COMMENT</span> <span class="token string">'项目附件表'</span><span class="token punctuation">;</span>

<span class="token comment">-- 查看建表语句</span>
<span class="token keyword">show</span> <span class="token keyword">create</span> <span class="token keyword">table</span> projectfile2<span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br></div></div><ul><li>AUTO_INCREMENT定义列为自增的属性，一般用于主键，数值会自动加1。</li> <li>如果你不想字段为 NULL 可以设置字段的属性为 NOT NULL， 插入数据为NULL ，就会报错。</li> <li>PRIMARY KEY关键字用于定义列为主键。 也使用多列来定义主键，列间以逗号分隔。</li> <li>ENGINE 设置存储引擎，CHARSET 设置编码。</li></ul> <p><strong>修改字段</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 添加字段</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token keyword">order</span> <span class="token keyword">ADD</span> code <span class="token keyword">CHAR</span><span class="token punctuation">(</span><span class="token number">6</span><span class="token punctuation">)</span> <span class="token keyword">DEFAULT</span> <span class="token boolean">NULL</span> <span class="token keyword">COMMENT</span> <span class="token string">'优惠码'</span>

<span class="token comment">-- 修改字段名</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> 表名 CHANGE 旧字段名 新字段名

<span class="token comment">-- 修改字段类型</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> 表名 <span class="token keyword">MODIFY</span> 字段名 字段类型<span class="token punctuation">(</span>字段长度<span class="token punctuation">)</span>

<span class="token comment">-- 删除字段</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> 表名 <span class="token keyword">DROP</span> 字段名
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br></div></div><h2 id="_5-索引">5.索引</h2> <h3 id="_5-1-创建索引">5-1.创建索引</h3> <p><strong>语法</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> 表名 <span class="token keyword">ADD</span> <span class="token punctuation">[</span><span class="token keyword">UNIQUE</span> <span class="token operator">|</span> FULLTEXT <span class="token operator">|</span> SPATIAL<span class="token punctuation">]</span> <span class="token keyword">INDEX</span> <span class="token operator">|</span> <span class="token keyword">KEY</span> <span class="token punctuation">[</span>索引名<span class="token punctuation">]</span> <span class="token punctuation">(</span>字段名<span class="token number">1</span> <span class="token punctuation">[</span><span class="token punctuation">(</span>长度<span class="token punctuation">)</span><span class="token punctuation">]</span> <span class="token punctuation">[</span><span class="token keyword">ASC</span> <span class="token operator">|</span> <span class="token keyword">DESC</span><span class="token punctuation">]</span><span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token keyword">USING</span> 索引方法<span class="token punctuation">]</span><span class="token punctuation">;</span>
<span class="token keyword">CREATE</span> <span class="token punctuation">[</span><span class="token keyword">UNIQUE</span> <span class="token operator">|</span> FULLTEXT <span class="token operator">|</span> SPATIAL<span class="token punctuation">]</span> <span class="token keyword">INDEX</span> 索引名 <span class="token keyword">ON</span> 表名<span class="token punctuation">(</span>字段名<span class="token punctuation">)</span> <span class="token punctuation">[</span><span class="token keyword">USING</span> 索引方法<span class="token punctuation">]</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><p><strong>示例</strong></p> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 添加PRIMARY KEY(主键索引)</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span> <span class="token keyword">ADD</span> <span class="token keyword">PRIMARY</span> <span class="token keyword">KEY</span> <span class="token punctuation">(</span> <span class="token punctuation">`</span><span class="token keyword">column</span><span class="token punctuation">`</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment">-- 添加UNIQUE(唯一索引)</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span> <span class="token keyword">ADD</span> <span class="token keyword">UNIQUE</span> <span class="token punctuation">(</span> <span class="token punctuation">`</span><span class="token keyword">column</span><span class="token punctuation">`</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment">-- 添加INDEX(普通索引)</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span> <span class="token keyword">ADD</span> <span class="token keyword">INDEX</span> index_name <span class="token punctuation">(</span> <span class="token punctuation">`</span><span class="token keyword">column</span><span class="token punctuation">`</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">CREATE</span> <span class="token keyword">INDEX</span> index_name <span class="token keyword">ON</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span><span class="token punctuation">(</span><span class="token punctuation">`</span>column1<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>column2<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>column3<span class="token punctuation">`</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment">-- 添加FULLTEXT(全文索引)</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span> <span class="token keyword">ADD</span> FULLTEXT <span class="token punctuation">(</span> <span class="token punctuation">`</span><span class="token keyword">column</span><span class="token punctuation">`</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token comment">-- 添加多列索引</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span> <span class="token keyword">ADD</span> <span class="token keyword">INDEX</span> index_name <span class="token punctuation">(</span> <span class="token punctuation">`</span>column1<span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token punctuation">`</span>column2<span class="token punctuation">`</span><span class="token punctuation">,</span> <span class="token punctuation">`</span>column3<span class="token punctuation">`</span> <span class="token punctuation">)</span><span class="token punctuation">;</span>

<span class="token keyword">CREATE</span> <span class="token keyword">INDEX</span> index_name <span class="token keyword">ON</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span><span class="token punctuation">(</span><span class="token punctuation">`</span>column1<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>column2<span class="token punctuation">`</span><span class="token punctuation">,</span><span class="token punctuation">`</span>column3<span class="token punctuation">`</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div><h3 id="_5-2-删除索引">5-2.删除索引</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 删除索引</span>
<span class="token keyword">ALTER</span> <span class="token keyword">TABLE</span> <span class="token punctuation">`</span>表名<span class="token punctuation">`</span> <span class="token keyword">DROP</span> <span class="token keyword">INDEX</span> <span class="token punctuation">`</span>索引名<span class="token punctuation">`</span>
<span class="token keyword">DROP</span> <span class="token keyword">INDEX</span> <span class="token punctuation">`</span>索引名<span class="token punctuation">`</span> <span class="token keyword">ON</span> <span class="token punctuation">`</span>表名<span class="token punctuation">`</span><span class="token punctuation">;</span>

<span class="token comment">-- 查看表上的索引</span>
<span class="token keyword">SHOW</span> <span class="token keyword">INDEX</span> <span class="token keyword">FROM</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h3 id="_5-3-查看索引">5-3.查看索引</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 查看表上的索引</span>
<span class="token keyword">SHOW</span> <span class="token keyword">INDEX</span> <span class="token keyword">FROM</span> <span class="token punctuation">`</span>table_name<span class="token punctuation">`</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><h3 id="_6-其他">6.其他</h3> <div class="language-sql line-numbers-mode"><pre class="language-sql"><code><span class="token comment">-- 查询有哪些库</span>
<span class="token keyword">show</span> <span class="token keyword">databases</span><span class="token punctuation">;</span>

<span class="token comment">-- 查询某个库下有哪些表</span>
<span class="token keyword">show</span> <span class="token keyword">tables</span><span class="token punctuation">;</span>
<span class="token keyword">SELECT</span> TABLE_NAME<span class="token punctuation">,</span>TABLE_COMMENT <span class="token keyword">FROM</span> information_schema<span class="token punctuation">.</span><span class="token punctuation">`</span><span class="token keyword">TABLES</span><span class="token punctuation">`</span> <span class="token keyword">WHERE</span> TABLE_SCHEMA <span class="token operator">=</span> <span class="token string">'manor_farm_mysql'</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div></div> <footer class="page-edit" style="display:none;"><!----> <div class="last-updated"><span class="prefix">Last Updated: </span> <span class="time">2020-12-18 6:27:50 PM</span></div></footer> <!----> <!----> <!----></main> <!----></div></div></div></div><div class="global-ui"><div class="back-to-ceiling" style="right:1rem;bottom:6rem;width:2.5rem;height:2.5rem;border-radius:.25rem;line-height:2.5rem;display:none;" data-v-c6073ba8 data-v-c6073ba8><svg t="1574745035067" viewBox="0 0 1024 1024" version="1.1" xmlns="http://www.w3.org/2000/svg" p-id="5404" class="icon" data-v-c6073ba8><path d="M526.60727968 10.90185116a27.675 27.675 0 0 0-29.21455937 0c-131.36607665 82.28402758-218.69155461 228.01873535-218.69155402 394.07834331a462.20625001 462.20625001 0 0 0 5.36959153 69.94390903c1.00431239 6.55289093-0.34802892 13.13561351-3.76865779 18.80351572-32.63518765 54.11355614-51.75690182 118.55860487-51.7569018 187.94566865a371.06718723 371.06718723 0 0 0 11.50484808 91.98906777c6.53300375 25.50556257 41.68394495 28.14064038 52.69160883 4.22606766 17.37162448-37.73630017 42.14135425-72.50938081 72.80769204-103.21549295 2.18761121 3.04276886 4.15646224 6.24463696 6.40373557 9.22774369a1871.4375 1871.4375 0 0 0 140.04691725 5.34970492 1866.36093723 1866.36093723 0 0 0 140.04691723-5.34970492c2.24727335-2.98310674 4.21612437-6.18497483 6.3937923-9.2178004 30.66633723 30.70611158 55.4360664 65.4791928 72.80769147 103.21549355 11.00766384 23.91457269 46.15860503 21.27949489 52.69160879-4.22606768a371.15156223 371.15156223 0 0 0 11.514792-91.99901164c0-69.36717486-19.13165746-133.82216804-51.75690182-187.92578088-3.42062944-5.66790279-4.76302748-12.26056868-3.76865837-18.80351632a462.20625001 462.20625001 0 0 0 5.36959269-69.943909c-0.00994388-166.08943902-87.32547796-311.81420293-218.6915546-394.09823051zM605.93803103 357.87693858a93.93749974 93.93749974 0 1 1-187.89594924 6.1e-7 93.93749974 93.93749974 0 0 1 187.89594924-6.1e-7z" p-id="5405" data-v-c6073ba8></path><path d="M429.50777625 765.63860547C429.50777625 803.39355007 466.44236686 1000.39046097 512.00932183 1000.39046097c45.56695499 0 82.4922232-197.00623328 82.5015456-234.7518555 0-37.75494459-36.9345906-68.35043303-82.4922232-68.34111062-45.57627738-0.00932239-82.52019037 30.59548842-82.51086798 68.34111062z" p-id="5406" data-v-c6073ba8></path></svg></div><!----><!----><APlayer audio="" fixed="true" mini="true" theme="#f9bcdd" loop="loop" order="random" preload="auto" volume="0.1" mutex="true" lrc-type="0" list-folded="true" list-max-height="250" storage-name="vuepress-plugin-meting" id="aplayer-fixed"></APlayer></div></div>
    <script src="/manor-farm-mysql/assets/js/app.bbd54b43.js" defer></script><script src="/manor-farm-mysql/assets/js/3.33fa8ee0.js" defer></script><script src="/manor-farm-mysql/assets/js/1.e501e4e7.js" defer></script><script src="/manor-farm-mysql/assets/js/33.ae9d6c1c.js" defer></script><script src="/manor-farm-mysql/assets/js/8.73e907b5.js" defer></script>
  </body>
</html>
